This section provides background information related to the present disclosure, which is not necessarily prior art.
Systems for delivering fuel to an engine, such as an internal combustion engine, often include a fuel reservoir pump, a low pressure fuel pump, and a high pressure (direct injection) fuel pump. The low pressure fuel pump pumps fuel from a fuel tank to the high pressure fuel pump. The high pressure fuel pump includes a reciprocating plunger, which is driven by a rotating cam (via a follower) having a plurality of lobes. As the cam rotates, it may cycle the high pressure pump through a suction stroke, a pre-stroke (if less than 100% fuel delivery is required), and a pumping stroke. The quantity of fuel that the high pressure pump delivers to the engine is based on engine demand and various engine perimeters, such as mass flow and pressure. Only an amount of fuel required to reach and maintain a commanded fuel pressure in a fuel rail of the fuel system is pumped out of the high pressure pump. When the fuel demand is less than 100% of pump capacity, excess fuel flow, such as during the pre-stroke, is pushed out of the high pressure pump through a pump inlet thereof, and into a low pressure fuel line that delivers fuel to the high pressure pump. Therefore, when engine demand is less than 100% of the high pressure pump's capacity, energy will be wasted operating the low pressure fuel pump to pump fuel to the high pressure pump that is not needed for engine operation.
The low pressure pump is typically operated as part of a Mechanical Returnless Fuel System (MRFS) or an Electronic Returnless Fuel System (ERFS). In a MRFS, a constant voltage is continuously applied to the low pressure fuel pump, which results in the low pressure fuel pump continuously pumping a fixed amount of fuel at a predetermined pressure. With an ERFS, voltage to the low pressure pump is varied depending on operating conditions of the engine in order to vary the quantity of fuel and/or pressure of fuel delivered to the high pressure pump. In both an MRFS and an ERFS, output of the low pressure pump is set to exceed engine demand in order to support continuous operation of the fuel reservoir pump, which pumps fuel from the fuel tank into a fuel pump reservoir in which the low pressure fuel pump is seated to keep the low pressure pump submerged in fuel.
Continuous operation of the fuel reservoir pump and the low pressure fuel pump at levels that exceed engine demand results in inefficiencies, including excess power consumption. A fuel system for delivering fuel to an engine, such as an internal combustion engine, which operates at reduced levels of power consumption and is generally more efficient than existing fuel delivery systems, would therefore be desirable.